Make a regression and copy/paste it into a graph on the Casio

Above is a slide from section 4.3 Loan Calculations and Regressions of the Financial Algebra textbook.  The numbers are from a workbook problem set.  It gave me the opportunity to work on the parent functions, talk about concave up vs concave down, curves vs. lines.  This activity charts a 20 year loan by the year.  They used the trace function and dual screen mode to pick out specific points between the given data points using the regression in dual screen mode.

Steps for making the regression:
1.  From the [menu] select stats.  In the stats menu, enter your data.

2.  Setup your graph--I wanted a scatter plot where List1=x and List2=y.  x is years, y is loan balance. We do this by pressing [f1] (graph) then [f6] set.  As you can see in the 3rd screenshot, it is set to scatter, L1, L2.  [exit] takes you back to your data set.  

3.  Now press [f1] for Graph #1 and  you see your scatter plot.  [f1] calc gives you the option to make a regression.  [f4] x^2 for quadratic.  It displays the quadratic shown above.  From here we can have the calculator automatically input the regression into the graphing application.  To do this we press [f5] copy.  It shows the list of equations, you scroll to which equation you want it to paste into and press [exe].  It goes back to the QuadReg screen, the equation has been placed in your graphing application.

4.  To access the new graph, [menu] shows an option for Graph.  Inside of there, make sure that your new equation is selected.  To do this, hover over it and press [f1] for select.  You can see it highlight the equal sign.  It should auto-fit the window but if not, you can press [shift][f3v-win] for window settings.  [exit] takes you back to the graphing, [f6] draw allows you to see it on the screen.

[f1] will allow you to trace.  If you wish, you can activate dual-screen mode by going into setup [shift][menu] and the third option says 'dual screen', [f2] g to t will give you a dual screen where by tracing [f1] and pressing [exe] twice adds values from the tracing to a table while still showing the graph.

*remember, that if the calculator is in 'dual screen' mode it cannot graph inequalities so it will need changed back through the same procedure.

As this semester continues and we explore more parent functions, I intend to work Dynamic Graphing into class and will post a how-to for that as well.

How to do monthly payment formula on Casio Fx-series

Monthly Payment formula is a tough calculation to do without math-type calculators.  In the old school this is how we had to do it:
Step 1

Step 2 (I couldn't include all of the calculations in one screen on the calculator)

[notice that the estimate is about 12 cents off.  This is because the irrational following the first exponential calculation was estimated to the nearest ten thousanth]

ENOUGH of this long OLD method for doing this.  

Introducting:  TVM Solver, standard on Casio Graphics (called Financial on newer models)

From the Menu, select TVM:  

Within the TVM Solver, we are using 'compound interest' which corresponds to [F2]

The shown values correspond to the given example visible in the earlier pictures.  Notice that I have keyed 12*4 into 'n'.  Casios have embedded calculating so students do not have to put 48 into this field, the calculator knows what 12*4 is.  Remember, this is a complete solver so you can solve for any of the variables given all of the other inputs.  This helps me work around logarithms associated with this relation of these numbers.  By inputting all other things, they can figure out what time horizon must be met in order for a loan payment to fit within a budget given an interest rate.  They can hypothesize about what happens when they adjust basis points for using automated bill-pay etc.  The way that they solve for these different variables is by selecting the one that they want from what is known as a 'soft menu' across the bottom, the f-keys correspond to the variables across the bottom of the screen.  

In this case we want to know the monthly payment given these conditions so we press [F4] 

Notice that I entered the principal as a negative.  If you don't do that then the payment shows as a negative.  This is part of the logic within this relation that if left alone would cause errors.  However, as you can see, monthly payment formula goes from a nasty calculation to an obstacle students can easily get over in order to get thinking critically about the meaning of these calculations.  

I followed this specific example up with a set of questions regarding the total interest paid, and different scenarios about how 'Mark' would do with a better interest rate, a cheaper car and a different time horizon.  To follow up with these, press [F1] to repeat, changing other conditions.